Matthews has been convicted more than a dozen times, serving several short jail stints. The sentencing requirement for most of his crimes is no more than 90 days in jail.

"We know he has a problem because he's been doing this for 20 years," said one of Matthews' neighbors, who was too afraid to give her name. "It's frightening because there are so many kids in the building. People need to be aware. It's disgusting and scary."

Despite his sordid history, Matthews' crimes aren't considered serious enough to put his name on any state registry - like the one that tracks sex offenders, sources said.

Yonkers cops conducted a manhunt for Matthews in August after he allegedly touched himself in front of two women near his Netherland Ave. apartment.

They finally found him last week, hiding under the blankets in his bedroom, sources said. Matthews is being held in lieu of $5,000 bail at the Westchester County Jail.

The ex-con's most recent busts by Bronx cops came in April and June, when he was arrested for masturbating in his car, cops said.

And in 2002, he was collared for allegedly exposing himself to three high school girls and a young woman in Yonkers, cops said.

When police nabbed him for that crime, they noticed that the rear seat of his car had been replaced with a comfy-looking bed, sources said.

"He got married a few years ago, and his wife knows he has issues," a neighbor said. "It's very sad."

Cops said a registry is needed to track repeat offenders like Matthews.